This invention relates to machine tools and more particularly to an anti-whip device for an elongated drive screw of a machine tool used to displace one component relative to another component of the machine.
In one type of conventional machine tool, there is provided a base member having a table portion on which a workpiece may be supported, a bridge or gantry member supported on the base member and adapted to be displaced relative to the base member along a longitudinal line of travel or what is commonly referred to as the x-axis, a tool head support assembly supported on the bridge member and adapted to be displaced relative to the bridge member along a transverse line of travel or what is commonly referred to as the y-axis, and a tool head assembly having one or more tools mounted thereon and engageable with a workpiece positioned on the table, supported on the tool head support assembly and adapted to be displaced along a vertical line of travel or what is commonly referred to as the z-axis.
Typically, the bridge members of such machines are displaced along the x-axis by a pair of elongated drive screws mounted on the sides of the base member which are operatively connected to the bridge member. Each of such drive screws is supported at its ends on bearings mounted in brackets secured to the base member, is driven by a motor mounted on the base member and operatively connected to an end portion of the drive screw and further is provided with a follower secured to the bridge member and operatively connected to the drive screw so that upon operation of the drive motor to rotate the drive screw, the interaction between the drive screw and the follower will cause the bridge member to be displaced along the x-axis.
Because such elongated drive screws are supported only at their end portions, the middle portions thereof tend to sag slightly, creating an out of balance condition when the drive screws is rotated, particularly at high speeds. As the drive screw is driven at higher speeds, the center thereof characteristically begins to swing in larger and larger circles until it reaches a critical speed at which point the drive screw vibrates violently, a condition which adversely affects the operation and longevity of the machine and which is sought to be avoided.
In the prior art, the most common solution for the problem of violent drive screw whipping has been to use larger diameter screws as the required lengths of the screws increase. With larger diameters, the screws sag less in the middle and can rotate faster without whip. The problem with the use of larger diameter screws, however, is that the cost of the screw and cooperating follower increases dramatically, and the mass and inertia of the screw increases requiring the use of larger and more expensive drive motors to maintain the performance of the system.
Accordingly, it is the principal object of the present invention to provide a novel means for preventing the whipping action of an elongated drive screw.
Another object of the present invention is to provide a novel means for preventing the violent whipping action of an elongated drive screw driven at high speeds.
A further object of the present invention is to provide a novel means for preventing the whipping action of an elongated drive screw without increasing the diameter of the screw.
A still further object of the present invention is to provide a novel means for preventing the whipping action of an elongated drive screw in a machine tool utilized to displace one component thereof relative to another.
Another object of the present invention is to provide a novel device for preventing the whipping action of an elongated drive screw in a machine tool utilized to displace one component thereof relative to another without increasing the mass and inertia of the crew requiring the use of larger drive motors in order to maintain the performance of the machine system.
A further object of the present invention is to provide a novel device for preventing the whipping action of an elongated drive screw in a machine tool utilized to displace one component thereof relative to another which is comparatively simple in design, relatively easy and inexpensive to manufacture and install and effective in performance.
Other objects and advantages of the present invention will become more apparent to those persons having ordinary skill in the art to which the present invention pertains from the following description taken in conjunction with the accompanying drawings wherein: